SEPA Flood Risk Standing Advice for Planning Authorities and … · 2020. 11. 18. · SEPA Flood Risk Standing Advice for Planning Authorities and Developers – Version 1 – November

SEPA Flood Risk Standing Advice for Planning Authorities and Developers

November 2020

SEPA Flood Risk Standing Advice for Planning Authorities and Developers – Version 1 – November 2020

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INTRODUCTION

This is standing advice from the Scottish Environment Protection Agency (SEPA) on flood

risk. Although this advice is principally aimed at planning authorities, developers will also

find it useful. All other standing advice can be found in our ‘Standing Advice for Development

Management Consultations’.

This document provides advice on a number of categories of development. Planning

Authorities should not consult us on proposals for these types of development, but

instead follow the advice provided. In some cases, local authority flood risk management

staff may require some aspect of flood risk to be investigated in a Flood Risk Assessment

(FRA). Provided that our standing advice is followed, SEPA should not be consulted.

Any type of development that involves landraising in the functional floodplain is not

covered by this standing advice, and SEPA should therefore still be consulted on such

proposals. Landraising is the process of raising ground levels in order to remove or partially

remove a site from an area of flood risk. Doing so reduces the ability of the functional

floodplain to store or convey water and can increase flood risk elsewhere.

This guidance excludes development consented under The Roads Scotland Act, or other

Acts of Parliament, Environmental Impact Assessment Regulations or developments

identified in the current National Planning Framework: SEPA should be consulted on such

development and will provide a bespoke response.

We may need to be consulted on some of these developments for reasons other than flood

risk (e.g. engineering works in the water environment). In such instances, this standing

advice still applies to the flood risk aspects affecting the development. More than one

category of standing advice may be applicable depending on the nature of the development

in question.

Developers should be aware that we regulate a number of matters that may be applicable to

development covered by this standing advice. To ensure proposals will meet all relevant

regulatory requirements, please refer to the authorisations and permits page of our website.

Best practice advice in relation to pollution prevention is available on the Net Regs website.

Scottish Planning Policy (SPP) (2014) states that the planning system should promote flood

avoidance by locating development away from functional floodplains. Planning authorities

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and developers should therefore be aware in their decision-making of the risks involved in

placing additional people and property at risk of flooding. The consequences of flooding can

be both temporary and long-lasting, tangible and intangible, and can include the following (in

no particular order of impact or severity), all, some, or none of which may be applicable to

the development types covered by this standing advice:

• Loss of human life.

• Impact on health, including mental health due to loss, disruption and concern over

future flooding events.

• Depreciation in property value and inability to gain future insurance cover.

• The need to relocate on a temporary basis (albeit this can be for several months or

years).

• Loss of, or damage to, personal possessions and property, including irreplaceable

items.

• Loss of, or damage to, utility supplies and transportation infrastructure.

• Loss of earnings.

• Loss of life to pets and livestock, and damage to crops.

STANDING ADVICE FOR PLANNING AUTHORITIES

For the categories of development listed overleaf, SEPA has no site-specific flood risk

advice. You should consult with your flood risk management colleagues for their flood

risk advice if required. Their advice should be taken into consideration when determining

the application. This standing advice should not be considered to constitute a formal

response from SEPA (i.e. an objection, non-objection etc.).

Any type of development that involves landraising in the functional floodplain is not

covered by this standing advice, and we should therefore still be consulted on such

proposals.

• Developments where the only source of flood risk is from surface water


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• Changes of use within a vulnerability category or to a lower category of vulnerability

(this includes developments in areas protected by a flood protection scheme), where

there is no change to the overall footprint of the development and the overall flood risk

has not increased

• Extensions of all sizes to single residential dwellings, including the provision of new

overnight accommodation/bedrooms but excluding the formation of an entirely new

dwelling

• The formation of new (or alterations and extensions to existing) garages, sheds,

conservatories, greenhouses and other buildings that are incidental to the enjoyment

of a main residential dwelling house

• Essential infrastructure or water compatible uses

• Cemeteries

• Small-scale street furniture (flagpoles, signage, benches, street-lights etc.)

• Walls, fences and other means of property enclosure/demarcation, including erection

of new and raising of existing structures. This does not include embankments if they

are not formally constituted under flood prevention legislation.

• Like-for-like replacement of watercourse crossings, culverts and bridges

• Hydro schemes

• Footpaths, access tracks, private roads, car parks and other landscaping proposals

(includes replacements and extensions)

• Open-sided agricultural buildings and structures (including poly-tunnels)

• Septic tanks and soakaways

• Temporary construction accommodation

• Reverse vending machines required to deliver Scotland’s Deposit Return Scheme

ADDITIONAL INFORMATION FOR LOCAL AUTHORITY FLOOD RISK

MANAGEMENT STAFF

The quick links below give additional information for local authority flood risk management

staff, which they may wish to refer to when providing advice on flood risk. If the local authority

requires an FRA to be carried out to assess any aspect of the proposal, SEPA’s Technical

Flood Risk Guidance may be useful to assist with obtaining or interpreting any such

https://www.sepa.org.uk/media/162602/ss-nfr-p-002-technical-flood-risk-guidance-for-stakeholders.pdfhttps://www.sepa.org.uk/media/162602/ss-nfr-p-002-technical-flood-risk-guidance-for-stakeholders.pdf


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assessment. Do not consult us for flood risk advice on proposals for these types of

development:

1. Developments where the only source of flood risk is from surface water

2. Changes of use within a vulnerability category or to a lower category of vulnerability (this includes developments in areas protected by a flood protection scheme), where there is no change to the overall footprint of the development and the overall flood risk has not increased

3. Extensions of all sizes to single residential dwellings, including the provision of new overnight accommodation/bedrooms but excluding the formation of an entirely new dwelling

4. The formation of new (or alterations and extensions to existing) garages, sheds, conservatories, greenhouses and other buildings that are incidental to the enjoyment of a main residential dwelling house

5. Essential infrastructure or water compatible uses

6. Cemeteries

7. Small-scale street furniture (flagpoles, signage, benches, street-lights etc.)

8. Walls, fences and other means of property enclosure/demarcation, including erection of new and raising of existing structures. This does not include embankments if they are not formally constituted under flood prevention legislation.

9. Like-for-like replacement of watercourse crossings, culverts and bridges

10. Hydro schemes

11. Footpaths, access tracks, private roads, car parks and other landscaping proposals (includes replacements and extensions)

12. Open-sided agricultural buildings and structures (including poly-tunnels)

13. Septic tanks and soakaways

14. Temporary construction accommodation

15. Reverse vending machines required to deliver Scotland’s Deposit Return Scheme

16. Glossary

1. Developments where the only source of flood risk is from surface water


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• All developments should consider how they will manage rain and surface water run-

off to avoid the risk of flooding to the new development, to adjacent developments and

to any watercourses where surface water is discharged. The CIRIA SUDS Manual

(C753) sets out how SUDS should be designed and constructed to meet all

requirements in relation to:

o Managing water quantity and flood risk (up to the 1:200 year event)

o Managing water quality

o Providing benefits for people and place by being integrated into and enhancing

the landscape quality and considered part of the wider green infrastructure

network

o Providing benefits for biodiversity

• The following points relate to the management of pre-existing surface water

flood risk only.

• Proposed developments with complex surface water hazards should ensure that the

surface water flood risk is adequately assessed and managed within the site boundary

(more strategic solutions are also acceptable provided they are able to be secured via

the land use planning process).

• SPP states that infrastructure and buildings should generally be designed to be free

from surface water flooding in rainfall events where the annual probability of

occurrence is greater than 0.5% (1:200 year). Local authorities are best placed to

assess and manage the different components of surface water flooding in relation to

new development, either directly as part of their existing responsibilities in relation to

roads and flood risk management, or collaboratively with Scottish Water where

Scottish Water intends to adopt any surface water management infrastructure.

• SEPA’s Flood Maps have a surface water flooding layer. It has been delivered to

planning authorities to support the consideration of such matters within the land use

planning system and they are publically available on our website. The map combines

pluvial sources and sewer model outputs to provide a strategic assessment of surface

water flood risk.

• Development should not take place within a flow path (i.e. natural, modified or SUDs

exceedance flow path), as this could increase flood risk to existing as well as new

https://www.ciria.org/ItemDetail?iProductCode=C753F&Category=FREEPUBShttps://www.ciria.org/ItemDetail?iProductCode=C753F&Category=FREEPUBShttp://map.sepa.org.uk/floodmap/map.htm


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development required. Note also that any landraising in areas where surface water

flows and ponds may only serve to increase flood risk to existing receptors by

deflecting water towards them.

• Residential development in lower ground/basement floors should be avoided where

surface water flood risk is significant and cannot be mitigated, as it can pose a risk to

life. This is due to potential rapid inundation where water could pour in from above

head height.

• Safe and flood free access and egress should be provided. This means the provision

of a safe and flood free route during the relevant flood probability event that enables

the free movement of people of all abilities (on foot or with assistance) both to and

from a secure place that is connected to ground above the design flood level and/or

wider area.

• We recommend that finished floor levels should be set 600mm above the design flood

level where appropriate and practicable in order to provide an allowance for freeboard.

• Developers should accept that buildings and other structures could be damaged

during a surface water flood event if they are located in or near to an area that floods.

They should therefore be designed to be flood resistant and resilient, as this will

mitigate the level of risk. Flood resilient buildings are designed to reduce the impact of

flood water entering the building so that damage is minimised. In comparison, flood

resistant buildings are designed to prevent or minimise the entry of water into the

building in the first place. The appropriate resilience and resistance measures will

depend on the characteristics of the design flood; this includes the estimated flow

velocity, inundation rate, depth that flood water will reach in the building and the

duration of the flood event. Specific guidance on flood resilient and resistant

construction techniques can be found in the CIRIA 2019 code of practice and guidance

for property flood resilience, and you may wish to consult with the local authority

building standards team regarding this issue.

• Where development is a replacement for existing development of the same type,

opportunities for flood risk betterment should be explored.

https://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBS


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2. Changes of use within a vulnerability category1 or to a lower category of

vulnerability2 (this includes developments in areas protected by a flood

protection scheme3), where there is no change to the overall footprint of the

development and the overall flood risk has not increased

• Safe and flood free access and egress should be provided where possible. This means

the provision of a safe and flood free route during the relevant flood probability event

that enables the free movement of people of all abilities (on foot or with assistance)

both to and from a secure place that is connected to ground above the design flood

level and/or wider area.

• A reduction in flood risk can be achieved through the incorporation of flood resistant

and resilient materials and design, and the raising of finished floor levels where

practicable. The CIRIA 2019 code of practice and guidance for property flood

resilience is a useful source of information and you may wish to consult with the local

authority building standards team.



We recommend that an allowance for climate change should be included when

calculating the design flood level, independently of an allowance for freeboard, as per

our Guidance on Climate Change Allowances for Flood Risk Assessment in Land Use

Planning.

• Developers should accept the risk that their structures could be damaged during a

flood event if proposing to build in or near an area that could flood, and should

therefore design them to be flood resistant and resilient. Flood resilient buildings are

designed to reduce the impact of flood water entering the building so that damage is

minimised. In comparison, flood resistant buildings are designed to prevent or

minimise the entry of water into the building in the first place. The appropriate

resilience and resistance measures will depend on the characteristics of the design

flood; this includes the estimated flow velocity, inundation rate, depth that flood water

will reach in the building and the duration of the flood event. Specific guidance on flood

1 Use our Land Use Vulnerability Guidance to establish the vulnerability of the existing and proposed land uses to flood risk. 2 Excludes changes to any residential/overnight use for (i) changes within a vulnerability category and (ii) lower categories of vulnerability. 3 As defined in SEPA’s Position on Development Protected by a Flood Protection Scheme.

https://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.sepa.org.uk/media/426913/lups_cc1.pdfhttps://www.sepa.org.uk/media/426913/lups_cc1.pdfhttps://www.sepa.org.uk/media/143416/land-use-vulnerability-guidance.pdfhttps://www.sepa.org.uk/media/306610/planning-information-note-4-sepa-position-on-development-protected-by-a-flood-protection-scheme.pdf


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resilient and resistant construction techniques can be found in the CIRIA 2019 code

of practice and guidance for property flood resilience, and you may wish to consult

with the local authority building standards team.

3. Extensions of all sizes to single residential dwellings, including the provision

of new overnight accommodation/bedrooms but excluding the formation of an

entirely new dwelling

• Extensions, even very small ones, have the potential to impact on local flood risk. They

can introduce more people to an area of flood risk, particularly during the night time,

and therefore increase the risk to life. They may also deflect water to other nearby

receptors. We recommend that these issues be carefully considered in the design and

decision-making process.

• A reduction in flood risk can be achieved through the incorporation of flood resistant

and resilient materials and design, and the raising of finished floor levels where

practicable. The CIRIA 2019 code of practice and guidance for property flood










We recommend that an allowance for climate change should be included when



Planning.






https://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.sepa.org.uk/media/426913/lups_cc1.pdfhttps://www.sepa.org.uk/media/426913/lups_cc1.pdf


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• We recommend that a 6m minimum (for channels less than 1m in width and increasing

proportionally to channel width) undeveloped buffer strip is provided in perpetuity

between all development types and watercourses, allowing space for natural fluvial

processes to occur (as well as other attendant environmental benefits, not limited to

but including biodiversity, open space, channel maintenance, pollution reduction and

river restoration). It is important to highlight that buffer strips do not mitigate any

identified flood risk that may exist at a site. Our guidance on the Water Environment

provides more information on buffer strips.

4. The formation of new (or alterations and extensions to existing) garages, sheds, conservatories, greenhouses and other buildings that are incidental to the enjoyment of a main residential dwelling house4

• Even small structures have the potential to impact upon flood risk elsewhere. We

recommend that these issues be carefully considered in the design and decision-

making process.

• Some structures can cause channel blockage elsewhere if washed out, exacerbating

local flooding. Structures should be installed securely to avoid potential wash-out in a

flood event. A reduction in flood risk can be achieved through the incorporation of flood

resistant and resilient materials and design, and the raising of finished floor levels

where practicable. The CIRIA 2019 code of practice and guidance for property flood



4 Includes extensions of all sizes that are not covered by Permitted Development Rights, but excludes the provision of new overnight accommodation/bedrooms and the creation of an entirely new dwelling.

https://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.sepa.org.uk/media/219894/lups-bp-gu2b-water-environment-planning-background-paper.pdfhttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBS


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level and/or wider area. We recommend that finished floor levels should be set 600mm

above the design flood level where appropriate and practicable in order to provide an

allowance for freeboard. We recommend that an allowance for climate change should

be included when calculating the design flood level, independently of an allowance for

freeboard, as per our Guidance on Climate Change Allowances for Flood Risk

Assessment in Land Use Planning.























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5. Essential infrastructure and water compatible uses5

• Such development should be designed and constructed to remain operational during

floods and not impede water flow.

• Consideration should be given to site layout and access, and alternative lower risk

locations sought for the most sensitive aspects of the development








• We recommend that an allowance for climate change should be included when



Planning.













• Developers and planning authorities should be aware that development at flood risk

may also increase the risk of flooding to nearby development and receptors.

5 Use our Land Use Vulnerability Guidance to establish the vulnerability of the existing and proposed land uses to flood risk. Essential infrastructure includes development consented under the Town and Country Planning (Scotland) Act 1997 only.

https://www.sepa.org.uk/media/426913/lups_cc1.pdfhttps://www.sepa.org.uk/media/426913/lups_cc1.pdfhttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.sepa.org.uk/media/143416/land-use-vulnerability-guidance.pdf


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• Where relevant, structures should be installed securely to avoid potential wash-out

during flood events.









6. Cemeteries

• Due to the sensitive nature of this development, consideration should be given to the

impact were the development to flood. Flooding could be from small watercourses

and/or groundwater, as well as larger fluvial and coastal sources. The long term

impacts of wave action and coastal erosion should also be considered for sites in

exposed coastal locations. Further information on coastal erosion can be found in

Scotland’s National Coastal Change Assessment.

• SEPA has published guidance on assessing the impacts of cemeteries on

groundwater. Groundwater is often the most significant constraint when considering

options for cemetery extension and assessing new sites.




Planning.






https://www.sepa.org.uk/media/219894/lups-bp-gu2b-water-environment-planning-background-paper.pdfhttp://www.dynamiccoast.com/https://www.sepa.org.uk/media/143364/lups-gu32-guidance-on-assessing-the-impacts-of-cemetries-on-groundwater.pdfhttps://www.sepa.org.uk/media/143364/lups-gu32-guidance-on-assessing-the-impacts-of-cemetries-on-groundwater.pdfhttps://www.sepa.org.uk/media/426913/lups_cc1.pdfhttps://www.sepa.org.uk/media/426913/lups_cc1.pdf


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therefore design them to be flood resistant and resilient.









• See also Section 8 below in relation to walls, which are a common feature of

cemeteries.

7. Small-scale street furniture (flagpoles, signage, benches, street-lights etc.)

• Such structures can cause channel blockage elsewhere if washed out, exacerbating

local flooding. Structures should be installed securely to avoid potential wash-out in a

flood event.














8. Walls, fences and other means of property enclosure/demarcation

• These structures can create an obstruction to flood flows and exacerbate local flood

risk. Where property enclosure/demarcation is required in areas at risk of flooding

https://www.sepa.org.uk/media/219894/lups-bp-gu2b-water-environment-planning-background-paper.pdfhttps://www.sepa.org.uk/media/219894/lups-bp-gu2b-water-environment-planning-background-paper.pdf


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then consideration should be given to alternative approaches to minimise the effect

on flooding, for example using open-structure fences instead of walls. Structures

should be installed securely to avoid potential wash-out in a flood event.

• Property walls should not be constructed with the sole intention of flood protection,

because they are unlikely to withstand the hydro-static pressure created during a flood

event. Furthermore, the sudden failure of a wall during a flood event can lead to rapid

and therefore more dangerous inundation. Instead, a more holistic and sustainable

approach should be adopted by identifying measures that can be incorporated without

increasing flood risk elsewhere, reducing the likelihood of failure of any one flood

protection measure. Property-specific protections should be the first step and include:

seeking insurance provision, signing up to Floodline to receive flood alerts, preparing

a flood plan, identifying an evacuation route (if possible), and property-level flood

protection products that could help to reduce the impact of flooding on property such

as airbricks and door guards. The Scottish Flood Forum can provide additional

information on preparing for flooding. The CIRIA 2019 code of practice and guidance

for property flood resilience is a useful source of information and you may wish to

consult with the local authority building standards team.




• Developers and planning authorities should be aware that development at flood risk

may also increase the risk of flooding to nearby development and receptors.

We recommend that a 6m minimum (for channels less than 1m in width and increasing








9. Like-for-like replacement of watercourse crossings, culverts and bridges

https://scottishfloodforum.org/https://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.ciria.org/ItemDetail?iProductCode=C790F&Category=FREEPUBShttps://www.sepa.org.uk/media/219894/lups-bp-gu2b-water-environment-planning-background-paper.pdf


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• Proposals for replacement culverts and bridges with structures that have identical

dimensions and gradient will not result in a change to local flood risk either upstream

or downstream.

• A good practice guide for river crossings can be found on the SEPA website.

10. Hydro schemes

• Powerhouses should be located as far back from the water corridor as is practicable,

and designed to be operational in times of flooding. We advise against the use of

protective flooding/landscaping bunds to achieve this.

• The construction of weirs to facilitate off-take mechanisms or the transfer of water from

one catchment to another may increase the risk of flooding locally if a nearby receptor

exists. We recommend that the developer demonstrates adequate mitigation of any

flood impacts. We also advise consultation with the local authority flood risk

management staff. Further advice is provided in SEPA’s Controlled Activities

Regulations (CAR) Flood Risk Standing Advice under ‘Discharge Alterations’.

11. Footpaths, access tracks, private roads, car parks and other landscaping

proposals – includes replacements and extensions.



therefore design them to be flood resilient.


opportunities for betterment should be explored.







identified flood risk that may exist at a site. There is potential for siting footpaths within

buffer strips to maximise their potential for leisure/nature access, whilst maintaining

their primary purpose. Our guidance on the Water Environment provides more

information on buffer strips.

https://d3n8a8pro7vhmx.cloudfront.net/yyccares/pages/16/attachments/original/1499142327/SEPA_River_crossings_-_good_practice_guide.pdf?1499142327https://www.sepa.org.uk/media/94134/car-flood-risk-standing-advice-for-engineering-discharge-and-impoundment-activities.pdfhttps://www.sepa.org.uk/media/94134/car-flood-risk-standing-advice-for-engineering-discharge-and-impoundment-activities.pdfhttps://www.sepa.org.uk/media/219894/lups-bp-gu2b-water-environment-planning-background-paper.pdf


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12. Open-sided agricultural buildings and structures (including poly-tunnels)

• Where it is deemed that a flood risk exists, local authority flood risk management staff

should be consulted and review any supporting information such as an FRA, where

necessary. Our guidance on carrying out an FRA will be helpful.

• These structures can cause channel blockage downstream if they are washed out,

exacerbating local flooding. They should be installed securely to avoid potential wash-

out in a flood event.

• Significant coverage of land by polytunnels may create localised flooding impacts in

the form of soil erosion and the runoff of water/ sediment onto rural roads. Impacts of

this type have been observed in recent times in a number of locations in Scotland,

particularly during summer months following intense rainfall events. Careful

consideration should be given to providing mitigation against such impacts, particularly

on sloping land.









13. Septic tanks and soakaways

• For pollution prevention purposes, we recommend that such development should

follow current Scottish Water guidance.

• Such structures should be installed securely to avoid potential wash-out in a flood

event.

• SEPA regulatory information on septic tanks and private sewage treatment systems

should be consulted.

https://www.sepa.org.uk/media/162602/ss-nfr-p-002-technical-flood-risk-guidance-for-stakeholders.pdfhttps://www.sepa.org.uk/media/219894/lups-bp-gu2b-water-environment-planning-background-paper.pdfhttps://www.scottishwater.co.uk/your-home/your-waste-water/septic-tankshttps://www.sepa.org.uk/regulations/water/septic-tanks-and-private-sewage-treatment-systems/


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14. Temporary construction accommodation6




Planning.

• Safe and flood free access and egress should be provided. This means the provision

of a safe and flood free route during the relevant flood probability event that enables

the free movement of people of all abilities (on foot or with assistance) both to and

from a secure place that is connected to ground above the design flood level and/or

wider area.


event.


flood event, and should therefore design them to be flood resistant and resilient.

15. Reverse vending machines required to deliver Scotland’s Deposit Return

Scheme


event.


flood event, and should therefore design them to be flood resistant and resilient.

TECHNICAL GLOSSARY

Betterment: Relates to achieving an overall flood risk reduction either via modification and/or

design (including use of flood resistant/ resilient materials) of a development. This can be in

relation to a new development or re-development of an existing building already at flood risk.

Catchment: The upstream area contributing to flow or runoff to a particular point on a

watercourse, i.e. all the land drained by a river and its tributaries.

6 Excludes the provision of overnight accommodation/bedrooms.

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Channel blockage: The full or partial physical blockage of a river channel (watercourse),

canal, flood diversion channel etc. from fallen trees, other woody debris, collapsed banks,

collapsed structures or other man-made detritus, including caravans, sheds and cars carried

off in a flood. Can often result in the backing up of water in the channel, leading to out-of-

bank flooding. Blockage often occurs on the upstream side of bridges and culverts, where

material gets lodged. Note that covered channels such as culverts, pipes and sewers can

also collapse or surcharge due to internal blockages.

Design flood level: The flood level (water level) associated with the specific magnitude of

flood adopted for the design of a development site, or flood protection scheme. It is usually

defined in relation to the flood severity or rarity, in terms of its return period or annual

probability. The SPP 2014 risk framework (para 263) suggests the most appropriate annual

flood risk probabilities for different land uses. For the majority of developments this will be

above the 0.5% annual probability flood extent or 200-year event (i.e. medium to high risk

areas). For the most vulnerable land use types this will be above the 0.1% annual probability

flood extent or 1000-year event (i.e. low to medium risk areas).

Duration (of flood event): Although self-explanatory, i.e. ‘the total amount of time an area

is affected by flood water’, it is important to understand that the longer the flood duration, the

greater the damage costs are. Damage costs similarly also increase with greater depth of

flooding. Increased duration also has a negative impact on the effectiveness of Property

Level flood Protection measures (PLP), such as air brick covers and door guards.

Evacuation: Involves the movement of people, either through their own efforts or with the

assistance of others, to a ‘place of safety’ without the need for specialist trained and equipped

rescuers. These activities take place before an area is inundated by flood water. Such egress

routes should be dry and free from flooding.

Flow path: The route(s) that flood water will take across natural or developed land (including

along roads or through buildings) generally following the path of least resistance, including

where water is deflected due to the presence of a notable feature/ structure. It also relates to

where water will go when a hydraulic structure fails or is exceeded, such as a SUDS pond,

detention basin or reservoir.

Flow velocity: Flow (or discharge) is the volume of water that passes through a channel

cross-section in a given unit of time, normally expressed as cubic metres per second (m3/s).

A flow velocity is the speed and direction of this discharge in meters per second (m/s). It can

also relate to overland flow from out-of-channel flooding, sewer surcharge or pluvial runoff.

Fluvial flood risk: the probability of a flood originating from a river (or other watercourse)

and of the potential adverse consequences, associated with it, for human health, the

environment, cultural heritage and economic activity.

Freeboard: A height added to the predicted level of a flood to take account of the height of

waves or turbulence and uncertainty in estimating the probability of the flooding. Industry

standard allowance is 600 mm. In a planning context, it can be the difference between the

design flood level and the finished floor levels of a development, or soffit /deck levels of a


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bridge or culvert. Freeboard is a common design element of formal flood defences, over and

above the required design flow and any additional allowance for climate change.

Functional floodplain: The floodplain is defined in SPP as the generally flat areas adjacent

to a watercourse or the sea where water flows in time of flood or would flow but for the

presence of flood prevention measures. The Functional floodplain refers to the role of

floodplains as areas of storage and conveyance for flood water. For planning purposes the

functional floodplain is defined in SPP as generally having a greater than 0.5% probability of

flooding in any year.

Hydrostatic pressure: Refers to the pressure exerted by any fluid in a confined space, due

to the force of gravity. Hydrostatic pressure increases with depth due to the increasing weight

of the fluid. Water is heavy and the increasing pressure of this water against a wall or

foundation, for example, can lead to water entering through the weakest point in the structure,

which can result in collapse. This potentially can apply to flood defence walls, culverts, dams

and buildings where, due to water depth, pressure can build up underneath the floor and

water can enter the property from below.

Inundation rate: This pertains to how quickly an area is being flooded, and how it may

change over time, e.g. the sudden collapse of a wall along a river, will result in more rapid

flooding/ inundation of the land behind the wall, than if the wall was not present. The rate of

flooding also depends on the discharge or magnitude of the flood source, whether it be from

a river, the sea, heavy rainfall or water behind a man-made structure, such as a flood defence

or a dam, which is somehow released.

Landraising: the process of raising ground levels in order to remove or partially remove a

site from an area of flood risk. Doing so reduces the ability of the functional floodplain to

store or convey water and can increase flood risk elsewhere.

Natural fluvial processes: The physical interaction of flowing water with the natural

channels of rivers and streams. Fluvial processes include the motion of sediment

(transportation), erosion, and deposition, leading to changes in river beds and banks. Fluvial

processes create a wide range of river forms, including meanders, pools, riffles and bars,

which provide a variety of habitats. Such natural processes can be interrupted or perturbed

by man-made structures in or on the banks of a river system.

Off-take mechanisms: Normally hydraulic structures sited to divert water from a river for a

specific purpose, such as hydro-power generation or water supply. They are very often

associated with a weir, e.g. lades, pipes, culverts, diversion channels, filter beds.

Open space: Space within and on the edge of settlements comprising green infrastructure

and/or civic areas such as squares, market places and other paved or hard landscaped areas

with a civic function. Detailed typologies of open space are included in Planning Advice Note

65.

Overland flow: The movement of water over the land, downslope toward a surface water

body (e.g. river or loch) or a low point in the land surface where it will pond. Overland flow is

a very important aspect of the water cycle and can be generated by different natural

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mechanisms, e.g. rainfall, snowmelt and soil saturation. Surcharge of man-made systems

can also generate overland flow.

Pluvial sources and sewer model outputs: These are the two elements that combine to

make up the Surface Water Hazard maps displayed on SEPA’s website, i.e. areas where

water will ‘pond’ from heavy rainfall (pluvial sources) and/or sewer surcharge, when the sewer

system is full and starts to spill. SEPA is responsible for modelling the pluvial flood hazard

from rainfall, whilst Scottish Water model the sewer risk. See also ‘Pluvial flooding’.

Pluvial flooding: Flooding as a result of notable rainfall, flowing over or ponding above the

ground before it enters a natural (e.g. watercourse) or artificial (e.g. sewer) drainage system,

or when it cannot enter a drainage system (e.g. because the system is already full to capacity

or the drainage inlets have a limited capacity).

Receptors: Categories of animate and inanimate objects (e.g. people or built development)

that can be adversely affected by a flood, e.g. under the Flood Risk Management (Scotland)

Act 2009, four key risk receptors are highlighted for which flood risk should be reduced, i.e.

Human Health, the Economy, the Environment and Cultural Heritage. Assets that fall under

Essential and Civil Infrastructure (as defined in SPP) would be important ‘receptors’ that may

be affected by flooding. For example, the National Flood Risk Assessment (NFRA) produced

by SEPA considers seven broad receptor categories – (1) Agriculture (land & buildings), (2)

Buildings (businesses, services and residential), (3) Community facilities, (4) Cultural

Heritage, (5) Environment, (6) Transport and (7) Utilities.

Surface Water Flooding: Same as ‘Pluvial flooding’ but also includes any surcharge/

spillage from a man-made sewer or water supply system, which causes water to flow

overland or pond above ground, in either urban or rural settings, creating a flood hazard.

Wash out (washed out): Refers to dislodgement of structures in or adjacent to a river

channel (or other flood source) during a flood event. Most commonly this term can be used

in relation to the destruction of roads and bridges during a flood, where they are said to have

been ‘washed out’ from their normal location.

Watercourse(s): All means of conveying water except a water main or sewer.


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Update Summary

Version Description

Version 1 New document to replace Appendix 2 of LUPS-GU8 - SEPA standing advice for planning authorities.

Notes

This document is uncontrolled if printed. Always refer to the online document for accurate and up-to-date information.

For information on accessing this document in an alternative format or language please email [email protected]

If you are a user of British Sign Language (BSL) the Contact Scotland BSL service gives you access to an online interpreter enabling you to communicate with us using sign language.

http://contactscotland-bsl.org/

www.sepa.org.uk

Strathallan House, Castle Business Park, Stirling, FK9 4TZ

SCOTTISH ENVIRONMENT PROTECTION

AGENCY Identifier:

LUPS-GU8

Land Use Planning System

SEPA Guidance

Pages: 22

Issue no: Version 1

Issue date: November 2020

SEPA Flood Risk Standing Advice for Planning

Authorities and Developers
mailto:[email protected]://contactscotland-bsl.org/http://www.sepa.org.uk/

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SEPA Flood Risk Standing Advice for Planning Authorities and … · 2020. 11. 18. · SEPA Flood Risk Standing Advice for Planning Authorities and Developers – Version 1 – November